The major objective of this study is to learn how environmental ultraviolet light interferes with the normal functioning of the ocular tissues. 1. Eyes of near-UV light exposed (300-400 nm) squirrels will be used as models for near-UV light effects on human eyes. Biochemical and anatomical studies of near-UV light effects on lens proteins, chromophores, enzymes, membrane stability and epithelial cell growth will be done. 2. Freely soluble and protein bound chromophores will be extracted from brunescent and pale nuclei and opaque and clear areas of human lenses for comparison; and on UV exposed and control squirrel lenses, HPLC, TLC, column chromatography, slab gel polyacrylamide electrophoresis, and optical methods will be used. 3. The effects of H2O2 and tryptophan UV photoproducts and near-UV light on in vitro lens epithelial cell protein synthesis, oxidation-reduction and ATPase enzymes of human and shark lenses will also be studied. 4. Fiber cell mmembrane stability of portions of brunescent and pale human lens nuclei and opaque and clear areas will be studied by SEM of extracted minced preparations and ease of protein extractibility by non-denaturing and denaturing solvents. 5. Photochemical changes in physical and chemical features of the vitreous humor and in morphology of the retina of aphakic squirrels exposed to near-UV light will be compared with those of normal eyes to discern if the absence of lens filtration enhances light damage to posterior tissues. 6. Cooperative Cataract Research studies of fresh human cataracts will continue in order to assess the role of external and internal factors on specific types of human cataract.